<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style type="text/css">
			html body{
				height: 100%;
				margin: 0px;
			}
			#a{
				width: 20%;
				background-color: red;
			}
			#b{
				width: 60%;
				background-color: yellow;
			}
			#c{
				width: 20%;
				background-color: blue;
			}
			#a,#b,#c{
				height: 100px;
				float: left;
			}
			
			#bottom{
				width: 100%;
				height: 300px;
				border: 3px black dashed;
				/* 消除浮动布局影响 */
				overflow: auto; 	
				/* left,right,both */
				clear: both;
			}
			
			ul{
				width: 300px;
				height: 300px;
				border: 1px black solid;
			}
		</style>
	</head>
	<body>
		<div id="outter">
			<div id="a">
				
			</div>
			<div id="b">
				
			</div>
			<div id="c">
				
			</div>
		</div>
		
		<div id="bottom">
			
		</div>
		
		<ul>
			<li style="float: left;">AAA</li>
			<li style="float: right; clear: both;">BBB</li>
			<li style="float: left; clear: both;">CCC</li>
			<li style="float: right; clear: both;">DDD</li>
		</ul>
	</body>
</html>
